This invention relates to remote manual and automatic hydraulic control systems and more particularly to such a system for controlling the elevation (height or depth) of a towed implement, such as a disc plow or a hay conditioner, for example, either manually from the tractor cab and/or automatically in response to the drawbar tension.
Heretofore the elevation of such implements has been set by a hydraulic cylinder which raises or lowers the wheels of the towed implement relative to its frame, thereby to raise and lower the implement relative to the wheels. The operator opens a valve supplying hydraulic fluid to the cylinder and leaves the valve open until the desired elevation adjustment is achieved; then the operator closes the valve. To change the elevation in the opposite direction a bleed valve is opened until the desired height is achieved, then the operator closes the bleed valve. Such setting of the elevation is imprecise and not accurately repeatable. Everytime the operator has to raise the towed implement, e.g. for crossing a road, travelling down the road to another field, crossing a ditch, or passing over a log or other impediment and then has to lower the implement to a working elevation, the working elevation will be a little different. If the towed implement hits an impediment such as a stump, rock or hard place, the resulting increase in drawbar tension may break the drawbar.
The purpose of the present invention is to provide the operator with precise, repeatable control of the working height or depth of towed implements such as disc plows, hay conditioners and others, where it is necessary to go from a transport height to a working height quickly and reliably. This is done remotely in the cab by the operator. A lever control with a graduated scale allows the operator to place the implement at the desired height or depth. No mechanical stops are needed on the implement. The height or depth is changed by simply moving the lever to another position. A feature of the invention is automatic working height or depth control as related to drawbar pull.